Near Field Communication (NFC) is a wireless technology that allows communication over a short distance, for example, 10 cm, between electronic devices, such as contactless chip cards or mobile telephones emulated in card mode, and readers. NFC technology is adapted for connecting any type of user device and allows fast and easy communications.
A contactless device is a device capable of exchanging information via an antenna with another contactless device according to a contactless communication protocol. An NFC device, which is a contactless device, is a device compatible with NFC technology.
NFC technology is an open technological platform standardized in the standard ISO/IEC 18092 and ISO/IEC 21481 but incorporates numerous already existing standards, such as, for example, the type A and type B protocols defined in the standard ISO-14443, which can be communication protocols usable in NFC technology. In addition to its typical telephone function, a cellular mobile telephone can be used (if it is equipped with specific components) to exchange information with another contactless device, for example, a contactless reader, by using a contactless communication protocol usable in NFC technology.
This makes it possible to exchange information between the contactless reader and secure elements situated in the mobile telephone. Numerous applications are thus possible, such as mobile ticketing in public transport (the mobile telephone behaves as a ticket or fare) or mobile payment (the mobile telephone behaves as a payment card).
Moreover, Europay Mastercard Visa (EMV) is an international security standard for payment cards of the chip card type that was initiated by the EMVCo consortium. Most, or indeed all, bank chip cards comply with the EMV standard as do most or indeed the entire pool of electronic payment terminals. Various sources describing the specifications of the EMV standard, in particular, version 4.3 of November 2011, are available from the EMVCo consortium.
Moreover, some specifications, entitled “EMV Contactless Specifications for Payment Systems” and comprising, in version 2.1 of March 2011 available from the EMVCo consortium, four books, deal especially with the contactless communication protocol used to perform bank transactions between two contactless devices, and in compliance with the EMV standard. The communication protocol for the contactless EMV standard is thus based mainly on the protocol described in the standard ISO/IEC 14443.
A contactless reader generally comprises a send/receive module, also called “radiofrequency head” (or “RF front end”) intended to be in proximity coupling with the contactless card or the mobile telephone emulated in card mode. This send/receive module is controlled by an external microcontroller, which is coupled by a bus to the send/receive module. The send/receive module receives the frames transmitted by the card, extracts the data bits (representing for example responses to commands) contained in these frames, and transmits them to the external microcontroller.
In the reverse direction; the send/receive module receives data bits (representing, for example, commands) intended for the card, encapsulates them in frames and transmits these frames to the card. The transmissions of information between the card and the reader may be marred by errors. One speaks of transmission error when an invalid frame is received, for example, when the modulation of the signal or the coding of the bits or the format (structure) of the frame do not comply with the specifications governing contactless communication between the card and the reader.
Some of these errors may be errors due to noise, for example, when the card is too far from the reader or when the microcontroller contained in the card generates the noise itself. This noise is also designated by the term “electromagnetic disturbance” (EMD). Moreover, it may be specified in certain cases, such as, for example, in the aforementioned specifications entitled “EMV Contactless Specifications for Payment Systems,” that certain transmission errors marring a response of the card are to be ignored by the reader and that the latter must then be capable of processing a new correct response of the card at the latest on expiration of a specified duration after the end of the response marred by the error that is to be ignored.
Other well defined transmission errors must on the other hand be processed by the reader, this generally causing the external microcontroller to dispatch a command to the send/receive module so as to reinitialize the magnetic field generated by the send/receive module inside the volume in which the card and the reader can communicate with one another.
The management of transmission errors, be it those that are to be ignored by the reader, in particular errors due to noise, or those that are not to be ignored so as to be processed, is a major issue for robustness of communication and reliability. Specifications of tests, for example, those contained in the document entitled EMVCo Type Approval Contactless Terminal Level 1, PCD Digital Test Bench & Test Cases, version 2.1a, October 2011, and available from the EMVCo consortium, have been established to ensure that the readers are capable of satisfying the specified requirements in the presence of disturbances of the EMD type.